Brighter days ahead. Doctor's Best Nutrition D3 contains Vitashine D3, a plant source of vitamin D3 (as cholecalciferol). Vitashine is made using a special extract of lichen - a small, unique plant species - and is delivered in the form of cholecalciferol, which is better absorbed by the body to deliver the best results. All the better since vitamin D plays an important role in most organs and systems of the body, regulates phosphorus and calcium levels for healthy bones and teeth, and helps provide optimal immune function.